IBS and SIBO

SIBO stands for small intestinal bacterial overgrowth. Depending on the journal article you read, SIBO can contribute to symptoms in 30-60% of IBS or Irritable Bowel Syndrome cases.

The bacteria that grows in the intestines are not typically the pathogenic type of bacteria we hear about in the news such as e.coli or clostridium.  They are typically relatively harmless bacteria except that there are so many of them that they start to cause problems.

Typical symptoms of SIBO include abdominal gas, bloating, pain, diarrhea and nausea. As you can see, there is a big overlap with IBS symptoms.

The gold standard of diagnosing SIBO is through a jejunal aspirate where they can fluid samples from inside your small intestine, but this test is not usually done in the clinic as it is quite invasive.  This test might only be done for research purposes.  Instead, one is usually given a SIBO breath test, or a methane/hydrogen breath test.  A typical protocol for testing would involve giving the patient some sugar-water to drink, then taking the patient's breath every twenty minute for up to 2 hours.  The breath is analyzed and if there is a high amount of methane or hydrogen gas, it forms the basis for diagnosing SIBO.  This breath test is not as sensitive as the jejunal aspirate so it will miss cases of SIBO.  It may not always be the case by hydrogen predominant breath tests are more often associated with diarrhea symptoms, while methane predomiant breath tests are more often associated with constipation symptoms.

We don't know what exactly causes SIBO but there are several hypotheses which include: (a) there might be some issues with gut motility so that food does not move in the gut--this could be caused by abdominal adhesions or scar tissue, or sometimes there is some extra length in the intestines causing blind loops; (b) there might be some disorders in the immune system so that the body tolerates larger amounts of bacteria than normal; (c) conditions where the bacteria in the large bowel are able to back-flow into the small intestine.

Typically, SIBO is treated with antibiotics.  The type of antibiotics used may depend on whether the breath test is hydrogen or methane predominant.  One type of antibiotic used is Rifaximin.  Some studies show it has the highest rate of efficacy. It is also a relatively "safe"  antibiotic to take because it is not absorbed by the body. Basically, the antibiotic just stays inside the gut and goes out through the stool.

In my practice, I have also asked patients with SIBO to stay on a low sugar or low carbohydrate diet for an amount of time so that there is no excess sugar to feed the growth of bacteria. In the meantime, and after the antibiotics, we also start to introduce probiotics methodically so that we can populate the gut again with good bacteria.  Over time, I have found that we have to be patient and strategic when we do this process because some patients' immune system is so sensitive to bacteria that even if you put in what is considered "good bacteria" like probiotics, they may still have gas and bloating.

I have also used herbs to treat SIBO, specially in cases where the patient does not want to use antibiotics or in cases where antibiotics do not offer long-term relief.  I have seen many patients who have done several rounds of different antibiotics which work for a few weeks or months but the symptoms return.  In this case, I try herbal medicine.  The studies to support the use of herbal medicine in treating SIBO is not as numerous or as robust as the ones which support the use of antibiotics, but there is definitely a place for its use.